The prevalence of obesity has been on the rise in the U.S. and the rest of the developed world for the last few decades. It is widely believed that obesity increases the risk of fat infiltration in, and accumulation around vital organs (heart, liver, kidney, pancreas, etc.), resulting in an inflammatory response that may lead to organ dysfunction and failure. Moreover, it is believed that as much as 14% of men and 12% of women within the normal body-mass index (BMI) range (20-25 kg/m2) have disproportionate fat build-up in and around abdominal organs. Infiltrated and visceral fat deposits have been associated with an increased risk of diabetic and cardiovascular diseases. Further, non-alcoholic steatohepatitis (NASH) has a clear association with hepatocellular cancer.
The most reliable non-invasive methods for the assessment of fat distribution and the quantification of visceral fat deposits involve magnetic resonance imaging (MRI) and computed tomography (CT) imaging. Similarly, proton magnetic resonance spectroscopy (1H-MRS) is considered to be the gold standard for the measurement of infiltrated (ectopic) fat in liver, muscle, heart and pancreas tissues, and has been validated against needle biopsies. Unfortunately, these techniques are not cost effective, and are usually not prescribed for a general body-fat composition assessment.
There are strong indications that the ectopic fat composition in the body (i.e. the visceral fat to subcutaneous fat ratio) and the percentage of fat infiltration in specific organs (liver, heart, pancreas) are strong predictors for metabolic and cardiovascular diseases. Early detection and intervention can slow disease progress, resulting in a more favorable prognosis. However, practical and cost-effective methods for the quantitative evaluation of ectopic fat composition do not exist.
Thermoacoustic imaging is an imaging modality that adds new insights into properties of tissues and other objects, above those offered by other established imaging modalities. Specifically, thermoacoustic imaging provides information related to the thermoelastic properties of tissue.
Unlike conventional ultrasound imaging, thermoacoustic imaging offers the advantage of an endogenous contrast for fat and fatty tissues due to their starkly lower electrical conductivity and permittivity in the radio frequency (RF) range compared to other water-rich soft-tissues.
The lower absorption coefficient in fat and fatty tissues compared to lean soft tissues, results in a strong contrast in the thermoacoustic absorption image that makes the fat regions appear darker compared to lean soft tissues.
Although techniques for determining fractional fat content of tissue have been considered, improvements are desired. It is therefore an object at least to provide novel methods and systems for determining fractional fat content of tissue.